The present invention relates to the field of receivers and transceivers for millimeter waves, such as used in millimeter-wave radar systems for example,
U.S. Pat. No. 5,263,193 discloses a heterodyne signal processing system that enables an intermediate-frequency (IF) signal detector to detect the electrical characteristics of millimeter and sub-millimeter wavelength electrical signals which have frequencies outside the operating range of the detector. Heterodyning signals entails mixing two frequency signals together to produce a heterodyne frequency signal which can equal the sum or difference of the frequencies of the first two signals. The millimeter wavelength signal is split into a first and second source signal with a power divider unit. The first source signal is frequency shifted to produce a frequency-shifted source signal. The first source signal is then used by any utilizing device of interest to produce a processed signal. The second source signal serves as a local oscillator (LO) signal. Finally a heterodyne mixer mixes the processed, frequency-shifted source signal with the LO signal to output an IF which is detectable by an ordinary IF signal detector.
U.S. Pat. No. 6,917,635 shows a method and system for producing radiation of a desired frequency with temperature invariance. Two or more radiation sources (such as laser diodes) that produce an output are included. A temperature difference between the sources is sensed and a temperature difference signal is produced. A control unit controls a heat flux to one or more or between two or more of the sources based on the temperature difference signal. The control unit may provide the heat flux by self-heating by a supplied current or by heater/coolers. The outputs of the two or more radiation sources are mixed in or on a nonlinear medium. The mixing of the outputs produces beat frequencies and a desired beat frequency or frequencies (in the millimeter-wave frequency region for example) may be selected by a resonant structure. The beat frequencies are invariant with fluctuations in ambient temperature.